Gum inhibitors for gasoline



Patented Feb. 1, 1938 UNITED STATES PATENT OFFICE GUM INHIBITORS FOR GASOLINE No Drawing. Application August 22. 1929,

Serial No. 887,787

15 Claims.

This invention relates to improvement in means for the protection of liquid hydrocarbon products against discoloration and formation of insoluble and gummy products, and more particularly to improved materials for use with unsaturated liquid hydrocarbons which may be used as fuels.

Liquid hydrocarbons as commercially produced, particularly when prepared by the distillation or cracking of petroleum, possess a tendency to discolor on standing and to form gums and resinous substances. Gasolines produced by the modern cracking processes are extremely complicated mixtures comprising many constituents, the character of these constituents and the relative proportions of different constituents depending upon the source of the crude and the particular cracking process employed. Besides the normal and branched chain parafllnes, there are often present substantial percentages of arcmatic hydrocarbons. The crude cracked gasoline also always contains unsaturated hydrocarbons, such for example as olefines and diolefines. These unsaturated compounds in the presence of air are capable of oxidation to form a series of products, some of which are resinous or gummy. The diolefines, and more unsaturated hydrocarbons, are particularly easily oxidized. Diiierences in structure other than the degree of unsaturation cause considerable variation in the tendency to oxidize, but in general the ease of oxidation increases with the degree of unsaturation. The more recent pressure methods of vapor phase cracking result in a considerably higher percentage of diolefines than the older meth ads, and it has been stated that these products may run as high as 8 to 15% in unrefined gasoline.

It has been necessary to treat the crude products resulting from the more recent cracking processes in some manner to remove the greater part of these more highly unsaturated products. Among these methods of treatment may be mentioned the sulfuric acid treatment and the fullers earth vapor phase treatment. While these methods of purification may remove the greater part of the highly unsaturated compounds, it is found that many brands of gasoline tend to discolor on storage and to form a certain amount of gum. The gum appears to bea complex mixture of polymerized hydrocarbons, resins, acids, aldehydes, ketones and peroxides. Its formation is distinctly detrimental in all cases. For example, the deposition of gum in gasoline gives a sticky substance which deposits upon the walls ('01. se s) and bottom of the container, and which may cause serious trouble if formed or deposited in ,the fuel system of internal combustion engines.

The soluble portion of the gum is also objectionable because of the introduction of a non-volatile component into the gasoline.

Our invention has for an object the inhibition of the formation of these insoluble gums and resins, with anattendant improvement in the quality of the gasoline and freedom from the dimcultles introduced by the formationof the more or less insoluble and sticky, gummy material, such as irregular gasoline flow in the fuel and lubricating systems of internal combustion engines. A further object is to make it possible to use as an internal combustion fuel, liquid hy drocarbons such as gasoline, that contain larger amounts of highly unsaturated compounds than commercially used at present. A product of this sort can be produced at a lower cost, and possesses in certain cases, improved fuel properties.

We have found that by treating liquid hydrocarbons, such as lubricating oils, transformer oils and hydrocarbon fuels, such as cracked gasoline or gasoline which has a tendency to form gum, with certain organic compounds the gum. formation can be very appreciably inhibited. More specifically, our invention relates to the use as gum inhibitors of compounds of the type reprein which R represents aryl or hydroxy aryl or aikoxy aryl groups and R represents a hydroxy sented by:

aryl or alkoxy aryl group. Preferably our anti- Z oxidants are used in small amounts, such as, forexample, between about .001% to 1%.

By way of example, if 0.03% of hydroxy diphenyl amine is dissolved in unrefined cracked gasoline, the formation of gum otherwise noticeable in the gasoline is very appreciably inhibited. By way of a laboratory test, the common method of measuring gum formation in a given gasoline is to evaporate 100 cc. of the fuel in a copper dish in a steam bath, and to determine the gum residue by the increase in the weight of the dish. When subjected to such a test the gasoline referred to in the example above gave the following results: a control sample of gasoline containing no added agent produced 392 mgm. of gum'per 100 cc., whereas a 100 cc. sample oi the same gasoline containing 0.03% of hydroxy diphenyl amine formed only 89 mgm. of gum per 100 cc. sample. The decrease in gum formation, because of the presence of the amine, was 77%. It will be understood that the example outlined above has been given merely for the purpose of illustrating our invention, and that we do not wish to be limited to the use of the specific inhibitor employed, to the concentration of inhibitor given in our example, nor to any particular type of hydrocarbon fuel. We may use higher or lower concentrations of any members of the class of compounds represented by the general formula and secure a markeddecrease in the formation of gum, although the decrease will vary depending upon the concentration of amine and nature of the hydrocarbon. v I

While we have found that hydroxy or alkoxy substituted secondary aromatic amines may be used to great advantage in inhibiting the 'formation of gums, numerous other amines falling within the class described by the general formula give good results. For example, we may introduce into the aryl radical represented by R or R in the general formula, a second hydroxyl or alkoxyl group, thus dihydroxy diphenyl amine, and para diethoxy diphenyl amine, for example, may be successfully employed to decrease the gum formation in hydrocarbon fuels. Oxy ethyl ortho anisidine may also be employed to decrease the formation of gum in liquid hydrocarbon fuels. We may use aryl, aralkyl and alkyl groups as substituents in the aryl radicals represented by R and R. in our general formula. Thus, R and B may be tolyl or xylyl radicals or their isomers, as well as phenyl or naphthyl groups. That is, for example, we may use p-lso propyl oxy phenyla-naphthylamine, p-lso propyl phenyl p-toluidine or 4'-OH dl tolyl amine. In the phenyl or naphtlrvl groups, in addition to alkyl substituents we may use hydroxyl or ethoxy radicals, or such radicals may be replaced by homologous alkoxy groups or their isomers, such as butyl oxy. propyl oxy or iso propyl oxy, etc.

In general, we have found that secondary aromatic amines containing as a substituent one or more hydroxyl groups, are effective gum inhibitors when employed with liquid hydrocarbon.

The amines which constitute our invention seem by virtue of their anti-oxidizing properties added, in an amount sufllcient'to'inhibit the formation of gum therein, a substance from the group consisting of compounds of the type:

R! NH/ normally tending to form gum to which hasbeen added, in an amount sumclent to inhibit the formation of gum therein, a secondary di-aromatic amine containing as a substituent'at least one hydroxyl group.

3. A motor fuel comprising cracked gasoline normally tending to form gum to which has been 5. A motor fuel comprising cracked gasoline normally tending to form gum to which has been added, in an amount sufilcient to inhibit the formation of gum therein, a dihydroxy diphenylamine.

6. Cracked gasoline to which has been added, in an amount suflicient to inhibit the formation of gum therein, a compound having the formula:

in which R represents a hydroxyl aryl or alkoxy aryl group.

7. Cracked gasoline .to which has been added, in an amount sufficient to inhibit the formation of gum therein, a compound having the formula:

i l-on in which R represents an aryl group and R represents a hydroxy aryl or alkoxy aryl group.

8. A cracked gasoline normally tending to deteriorate and develop gummy substances on storage and containing an amino phenol in which an amino hydrogen has been substituted by an aryl radicle in quantity sufflcient to retard such sum formation.

9. A cracked gasoline normally tending to form gummy substances on storage and having incorporated therein in an amount sufficient to retard such gum formation a secondary aromatic amine containing at least one alkoxy substituted aryl nucleus.

10. A cracked gasoline normally tending to form gummy substances on storage and having incorporated therein in an amount suiilcient to retard such gum formation a diarylamine in which one aryl group contains an alkoxy group.

11. A cracked gasoline normally tending to form gummy substances on storage and having incorporated therein in an amount sufllcient. to retard such gum formation a diphenylamine in which one phenyl group contains an alkoxy roup. v

12. A cracked gasoline normally tending to form gummy substances on storage and havin incorporated therein in an amount sumcient to retard such gum formation a diarylamine in which one aryl group contains an ethoxy group.

13. A motor fuel comprising cracked gasoline, normally tending to form gummy substances on storage, to which has been added a hydroxy diphenylaminein an amount sumcient to inhibit the formation of the gummy substances.

14. A motor t'uel comprising cracked gasoline,

normally tending to form gummy substances on storage, to which has been added an amino cresol in which an amino hydrogen has been substituted by an aryl radical in an amount suflicient to inhibit the formation of the gummy substances.

15. A cracked gasoline normally tending to form gummy substances on storage and having incorporated therein in an amount suflicient to retard such gum formation a compound having the formula i R-N-R wherein R represents an aryl group and R represents a member of the class consisting of hydroxy-substituted aryl groups and alkoxy-substituted aryl groups.

' HAROLD WALTER ELLEY.

HERBERT W. WALKER. 

